This invention relates to a sensor for sensing the displacement of a body and in particular to a sensor which is suitable for use in hostile environments where direct contact with the body is undesirable.
It is known for displacement to be sensed using a follower device such as disclosed in U.S. Pat. No. 3,065,635 in which a magnetic follower is isolated from the body but moves in unison with the body by virtue of magnetic coupling. The displacement of the follower device is then taken as an indication of the body's displacement.
Such sensors have particular application to measurement of liquid levels where the body constitutes a float.
It is also known from U.S. Pat. No. 4,637,254 to provide a position sensor in which a deformable strip adopts an S-bend configuration at a localized position along its length and the position at which the S-bend is formed is determined by the position of a body whose displacement is to be sensed. The position at which the S-bend is formed is then detected as an indication of body position. A disadvantage of this system is that the body is biased into contact with the strip in order to deform the strip and a flexible seal arrangement is required to protect the sensor from the environment in which the body is movable.